Both the AM and GT Models are designed for use with atmospheres.  GT Models are designed with a continuously welded furnace shell, gasketed door assembly, and atmosphere inlet and outlet ports for operation with a positive flow of higher atmosphere rates.  GT Models are best suited for constant operation to maintain a dry refractory environment in the work area to minimize oxidation on workloads.  GT Models are a less expensive alternative compared to AM Models

AM Models are equipped with an alloy muffle and can operate with inert or flammable protective atmosphere.  Use with flammable atmsophere requires the addition of an Atmosphere Safety System per NFPA Code 86C.  With the AM Models there is a positive flow of protective atmosphere.  The alloy muffle separates the chamber refractory and heating elements from the workload and atmosphere to minimize scale and oxidation on most tool steels.  The design of the AM Models achieves lower dew points, reduced atmosphere consumption and shorter purge times.